Various techniques for attacking another user's assets during play of an online game are known. For example, in a tower defense game, a user may send a set of virtual units controlled by the user to attack and/or destroy one or more virtual units, structures, and/or other assets of another user. Conventional systems restrict a set of virtual units that may be sent to attack another user to include virtual units of the same type. In that way, game logic of a conventional system may easily determine the consequence of an attack of the set of virtual entities. Conventional systems, however, fail to enable a user to select various types of virtual units to include in a single attack on another user's assets in a tower defense game. Conventional systems suffer from these and other drawbacks.